Interest on delayed excise duty accrual and calculation rules, including exceptions for voluntary payment and appellate adjustments. Interest liability attaches where excise duty is unpaid, short paid or erroneously refunded; interest at government fixed rates accrues from the first day of the month after the duty fell due or from the date of erroneous refund until payment. A voluntary payment exception relieves interest where duty arising from a Board order is paid in full without reserving appeal rights within the prescribed period; otherwise interest applies to the entire amount. Interest is recalculated to reflect appellate or judicial adjustments, charging interest on reduced or increased duty as determined on appeal. The provision excludes duties falling before the referenced Finance Bill date.